1. Technical Field
The present invention relates to an external storage device designed to be attachable to and detachable from a host; and to a method of controlling the device.
2. Related Art
In the field of external storage devices (e.g. hard disk drives, USB memory, etc.), it is known to connect devices to a computer, printer, or similar device (a “host”) utilizing a connection interface that supports hot plugging, such as the USB interface. By connecting such an external storage device to a host, data can be read from or written to the device; an added convenience is that the data is also portable. However, such external storage devices pose the risk that, if left unguarded with data stored therein, the data stored in the device may fall into the hands of others.
In the case of storage devices having password functionality based on the ATA standard for example, this issue is addressed by having the system BIOS generate a password, saving the password, and then using this same password to lock and unlock the device when starting up or shutting down the host computer. With regard to the external storage device, one proposed design detects when the power is turned on, and when the power has been turned on, the entire hard disk drive can be unlocked with the aforementioned password through an ATA security lock command; and when the power is turned off, an ATA security lock will be placed on the device (See, e.g., Japanese Publication No. 2007-35136).
However, in the prior art discussed above, due to the fact that the security lock is placed on the device only when power to the device is shut off, even if the host has been shut down a security lock will not be placed on the external storage device if the power to device has not been turned off. A resultant problem for external storage devices having an external power supply is that, after shutdown of the original host, if another host is connected to the external storage device with the device remaining connected to the external power supply, it may be possible to access data on the device, due to the fact that the power has not gone off and the security lock has not been applied, despite switching of the host.
An advantage of some aspects of the present invention is to make it possible to limit access to data in an external storage device in the event the connection from the host has been lost, even if power to the device has not been turned off.
The entire disclosure of Japanese patent application No. 2009-091482, of Buffalo is hereby incorporated by reference into this document.